Electric furnace.



PNTTED STATES PATENT @FFTCEQ ALLEYNE REYNOLDS, OF LONDON, ENGLAND.

ELECTRIC EURNACE.

Application led. February 10, 1908.

To all whom t may concern:

Be it known that I, ALLEYNE REYNOLDS, a subject of the King of GreatBritain, residing at ll Queen Victoria street, in the city of London,England, consulting metallurgical engineer', have invented certain newand useful Improvements in Electric Fun naces, of which the following isa specification.

For the economical working of electrically heated furnaces it isimportant that the ratio of the radiating and conducting surface to thevolume of the charge should be as small as possible; that the heatshould be applied either uniformly throughout the charge or to thatportion of the charge in the bottom of the furnace, and that thiscondition should hold good irrespective of the quantity of the charge.

The object of the present invention is more particularly to secure thelatter of these conditions of economical working by using one -or moreelectrical heating elements which may be immersed in the charge. Theseheating elements consist of a close ended tube or pot of carbonaceousmaterial, preferably plumbago, or of a tube of such material closed atthe bottom by a carbon plug, forming one electrode, and of a carbon rodor rods within the tube forming the other electrode, the heat beingproduced either by arcing between the carbon rod and the carbon plug, orthe bottom of the pot as the case may be, or a carbon rod sealed in thebottom of the pot or by means of an imperfect electrical conductor, suchas loose carbon or a mixture of loose carbon with other material ofgreater resistivity or a solid resistance of carbon or of a carbonmixture, which bridges the space between the two electrodes.

The interior of the plumbago tube may be lined with an electricallyinsulating but thermally conducting refractory material such ascarborundum or siloxicon, and the outside.' may be incased if necessarywith any suitable refractory material which is inert to the charge or tothe material of the furnace walls, as the case may be, at workingtemperatures.

In the accompanying drawings Figure 1 is a central vertical section of afurnace embodying the present invention, Figs. 2 and 3 are similarsections of slightly modi- Specification of Letters Patent.

Patented Sept. 28, MMM.

serial No. 415,194.

lied constructions of electric heating elements; and Fig. 4L is a partsection of a furnace showing a tubular heating element embedded in thefurnace floor.

In the form shown in Fig. l, a plumbago pot is formed with an internalledge 2 upon which rests a sleeve 3 of refractory insulating materialsuch as magnesite, silicate of alumina, or other suitable substance ormixture, which encircles and guides the carbon electrode t by which thecurrent is introduced to the heating element. The electrode t issuitably supported externally to the pot, preferably by means whichadmit of adjusting its position vertically in the usual manner. Thesleeve 3 and particularly the lower portion thereof may, if necessary,be made of a more refractory material such as carborundum or siloxicon.A carbon rod 5 is secured in electrical Contact with the bottom of thepot by suitable means as a ramming 6 consisting of a mixture of groundcarbon and tar, or a bed of dry loose carbon may be substituted for thecarbon rod and ramming. The electrical connection to the plumbago pot lmay be conveniently made by ramming a mixture of finely ground earbonand tar between the rim of the tube and a metal ring 7 encircling it,and these parts are preferably formed with cooperating ledges as shownand the metal ring and attached connections are preferably made heavyenough to prevent flotation of the element when immersed in the charge.A cover plate or straps as indicated at 7l secured to the ring 7 afterthe joint is made and extending over the rim of the tube serve to holdthe latter in position in the ring. In this construction thc heat isgenerated by an are struck between the electrode 4 and the carbon rod orfilling in the bottom of the pot which constitutes the other electrodeand since the arc is practically completely cut off from access of airthere is a comparatively slow consumption of the carbons and the wholeof the heat generated is, with the heating element immersed in thecharge, absorbed entirely by the charge.

In Fig. l, 21 denotes the furnace casing, 22 the furnace lining ofsuitable refractory material, 23 the tap hole and spout, 24E the lid and25 the refractory lining of the lid. The lead from the positive pole ofthe source of current is shown as secured in a socket in the metal ring7 by means of one of the eye bolts 26 by which the heating element islowered or raised.

The construction of Fig. Q is substantially identical with that of Fig.l with respect to the parts indicated by the same reference numerals,but in this case the interior of the pot l is filled with broken carbon8 or other suitable imperfect electrically conducting medium and theheat generated inthis resistance. rlhe resistance of tli'e carbonfilling 8 lwould in general be much too small in thecase of pots ortubes of dimensions suitable for the purpose intended and consequentlysome means are required for grading` the resistance by reducing theaverage cross section or increasing the average length of the pathavailable to the current. Fig. 3 shows a construction in which boththese means are employed. rThe cross section available for the resistingmedium is reduced and the average length of the path increased by liningthe lower portion of the pot walls with a refractory insulating materialf) which is also a good conductor of heat, preferably with a carbid ofsilicon or silica, such as carborunduin or siloXicon. A further increaseof the resistance of the element is obtained by embedding in theresisting medium a rod or rods of blocks such as 10 of a similarmaterial, rEhe outside of the plumbago tube or pot may be incased in asuitable refractory material as indicated at 5), this material beingpreferably inert to the charge, or it may be of the same material as thefurnace lining 22. It will be understood that the internal and theexternal linings O, 9 may be applied to the other constructions shown inthe drawings.

The heating element may also be constructed as a plumbago tube havingits lower end closed by a carbon plug, such a construction beingpreferable if the heating element is to be inserted or embedded, forexample, in the floor of the furnace. In such a case, as shown in Fig.et, the plumbago tube 1G is'centered in an annular plate or ring 12which may be a portion of the furnace casingor may be insulatedtherefrom. rl`his ring is closed by a cap lil and the spaces l-l, 15outside and inside the end of the tube are rammed up to the level of thefurnace casing with a sealing material which is electrically conductivesuch as a mixture of ground carbon and tar.

llaving thus described the nature of this invention and the best means Iknow of carrying the same into practical effect, I claim:-

l. For the generation of heat electrically in metallurgical furnaces, anelectric heating element comprising a tube of carbonaceous materialimmersed in the furnace charge, means for closing the ends of the saidtube, means for conducting an electric current to the interior of thetube, and means for converting electric energy into heat within the saidtube, substantially as described.

2. For the generation of heat electrically in metallurgical furnaces, anelectric heating element comprising a plumbago pot immersed in thefurnace charge, a sleeve of electrically insulating refractory materialsupported in the upper portion thereof, a carbon electrode guided by thesaid sleeve within the pot, and means for conveying current to the potand the said electrode, substantially as described.

3. For the generation of heat electrically in metallurgical furnaces, anelectric heating element comprising a plumbago pot immersed in thefurnace charge, and means for producing and maintaining an electric arcwithin the said pot, substantially as described.

t. For the generation of heat electrically in metallurgical furnaces, anelectric heating element comprising a plumbago pot iminersed in thefurnace charge and having an internal lining of electrically insulatingbut thermally conducting material, and means for generating heat withinthe pot, substantially as described.

For the generation of heat electrically in metallurgical furnaces, anelectric heating element, comprising a plumbago pot immersed in thefurnace charge and a metal ring encircling and having a ledge supportingthe upper end of the pot, said metal ring being connected electricallywith the pot by a luting of finely ground carbon and tar rammed into thespace between the metal ring and the rim of the pot, substantially asdescribed.

In testimony whereof I have signed my name to this specification 'in thepresence of two subscribing \\'itnesses.

AL'LEYNE ,REYN OL'DS.

lVitnesses Ouvrir. ISMAEL, A'Lrimn PlonN MAXWELL.

